This is the basis of the story but it will take many many chapters to get there. I am starting with their first year and working my way through it. Whilst my tags say no bashing I will point out how bad friends everyone can be and no I will no be redeeming Draco.
They should not be doing this; they know it. Getting pissed out their minds so soon after deciding to end their relationships will only end in bad decisions. They've got no thoughts on how much is too much and thank Gods they're not out at a club or a pub because they'd surely be kicked out by now. It doesn't matter that he's Harry The-Boy-Who-Lived Potter and she's Hermione The-Golden-Girl Granger, they're both so far past drunk that even Aberforth would have no choice but to send them packing. It's been exactly 6 weeks since the war ended and after 6 weeks both Harry and Hermione had given up on trying to make their relationships with Ginny and Ron work.
Why Hermione thought it would ever work will never make sense to anyone but her; her and Ron are just too different. All you had to do is watch them throughout their time in the common room to see how different they are. That's if Hermione were even in the common room that is, she could usually be found in the library and Ron well he'd be sat either playing exploding snap or chess although Hermione could never look at a chess set again after the end of their first year. She was studious whereas he had to be bargained with to even produce a simple piece of homework let alone study for his exams. He loved the idea that during the Horcrux hunt there would be no work, yet Hermione hates the fact that she missed out on her final year even if it was to end that blasted war. She would rather have been given all the information before Dumbledore died and dealt with it in the summer so that she could get her N.E.W.T.S.
Harry's situation was much the same; well not exactly the same just the same in that he doesn't understand why it took him 6 weeks to decide it wasn't going to work when he knew that back at the end of his sixth year. He can tell people that he broke up with Ginny back then to protect her because of the war but he knows deep down that people still made their relationships work during the war. Just look at Bill and Fleur, they literally got married in the middle of the war and they're still going strong, she's been his rock since Fred died if anything. Then there's Remus and Tonks; damn it hurts to think of them. Remus may have needed slapping upside the head once he found of Tonks was pregnant and he tried to run out on her (Sirius would be so proud of how Harry managed that he thinks) but everyone could see how madly in love they were. Tonks was only at the battle because she didn't want her husband to be without her that night.
So, it's not like Harry and everyone else believes that relationships had to end because of the war but Harry knew he couldn't bring himself to hurt Ginny just before he went on the Horcrux hunt especially as he didn't know whether he'd make it out of it alive. And if were being honest there's too many times Harry almost didn't make it out of it. Firstly, the ministry break-in, then the starvation (this one didn't affect Harry as much as the other two thanks to the Dursleys), then there's the stupid snake at Godric's Hollow, then there's the frozen lake that Ron saved him from, then we can add Malfoy manor he thinks but Hermione definitely suffered more, the break in to Gringotts, the damn battle; oh lets not forget the fact he yet again technically survived a good old killing curse of old Tom himself even if he did technically die. So yes, telling Ginny that he didn't want her worrying about him was much better than saying he just doesn't have feelings for her but that doesn't explain why he went back after the war. Could he blame the come down of emotions of why he went back? He definitely could blame that it was something familiar for why but really it's because he's a coward, a big fat coward who when he realised his feeling for his female best friend waited and let her get with someone who definitely didn't suit her and now that they're both single he's still a massive coward; because why would he ever tell her?
Well… the alcohol certainly thinks he should tell her. He tries to stop himself all night and succeeds right up until the end. She looks so broken like she's about to cry, and he cannot stand to see her like that. What he doesn't realise is that she's actually just trying not to tell him that he looks so damn fit tonight that she keeps biting her cheek and its starting to hurt. To Hermione being alone with Harry is asking for trouble. It was fine when they were in the tent because she could put her emotions into the anger at Ron for leaving them and for being a dick about it. But here both single again she cannot deny just how attractive he is. They've both regained some of the weight they'd lost when Madam Pomfrey decided that she wasn't even entertaining them not being seen by a healer that deals with weight the day after the war ended. She at least gave them a dreamless sleep recognising that they were magically exhausted. They were quickly put on nutrition potions and damn Hermione thinks she's never seen Harry look so good. Not only has he gained some weight, but his muscles look more defined than she's ever seen them and is damn clothes fit him properly. She's never seen him in clothes that fit him because his robes are usually larger to fit him throughout the year and his non-wizarding clothes are so large you could fit them both in them. And now she's blushing like a girl with her first crush and if you wanted to be technical, she is as Harry was her first crush.
She realises she's had enough and goes to get up before she passes out right here on the sofa but as she does her legs feel like jelly and she falls face first onto him. Right onto his lap, where he's in joggers and apparently the alcohol has him not so very soft. He helps her straighten herself out, but she hears him mumble this only happens in my dreams as he does. And now she's confused because what only happens in his dreams? Her making a fool of herself, because she does that all the time, she may be smart but that's only out of books she's socially awkward at the best of times. So of course, she decides to make it even more awkward; well, the alcohol does and forces her to call him out on it.
"What only happens in your dreams?" at least she hopes it sounded like that because she can't exactly hear herself over the alcohol rushing in her bloodstream.
"Erm well, I mean. You falling in my lap" he says looking down at his lap. Oh, fuck why did he say that he could have said literally anything else but no now he's made a fool of himself. He's sure his friendship has been ruined. All he had to do was keep his mouth shut. It's not like she's gonna have the same dreams, him and Ron are nothing alike; he's also nothing alike Victor. Literally the only thing they all have in common is quidditch. Looking back up at her he sees her eyes wide and if he looks closely, he'd see the hope written on her face and the way she's holding herself.